1. Field of the Invention
The present invention relates to a method of embedding a watermark into a digital image, and more particularly, to a method of embedding a watermark into an image in a manner that the embedded information is robust against any modifications including loss data compression, filtering, channel noise, cropping, geometrical transformations, and etc.
2. Discussion of the Related Art
Digital images are widely distributed on the Internet or with uses of many types of storage such as CD-ROM, hard and floppy disks, and etc. Therefore, the copyright protection of such digital images has become a very significant issue in the current digital media industry. One of ways of preserving the intellectual property rights of the digital images is digital watermarking.
One of typical digital watermarking methods is a statistical approach, which will be referred to as Patchwork hereinafter. Patchwork is based on a pseudo random and statistical process. It invisibly embeds a set of specific statistical information that has a Gaussian distribution into a host image. Some of main features of this approach are an extremely low rate of the embedded data and difficulties of decoding a watermark in the presence of severe affine transformation.
Another digital watermarking method is a spread spectrum technique, which proposes to embed watermark information in a log-2-spatio domain by using a spread spectrum technique. In the log-2-spatio domain, the variance of the information is significantly reduced. This improves the efficiency and robustness of spread spectrum technique. Low intensity and mid-band regions are selected to embed the information in order to guarantee the invisibility of the watermark as well as the robustness to JPEG compression.
Also, an effect that a channel coding process produces on the performance of the watermarking detection is analyzed. However, the mentioned methods or techniques do not achieve the main demands for watermarking, which are invisibility of watermarks and robustness to attacks including loose compression, filtering, geometric attacks such as re-sampling and rotations, and so on.